On Airflow Assisted Printing Of Flexible Organic Field Effect Transistor And Its Applications

As a sort of key element of large-scaled and integrated flexible electronics,flexible organic field effect transistors(OFETs)have broad application prospects in flexible displays,information communication and flexible sensors.In view of the difficulties to obtain OFETs with high carrier mobility under patterned fabrication methods such as electrospray,EHD printing,etc.and the OFETs currently reported show high operating voltage,we demonstrated poly(3-hexylthiophene)(P3HT)semiconductor layer based flexible OFETs which were fabricated by airflow assisted printing.Thanks to the shearing effect caused by the substrate’s movement and airflow,the crystallization property of P3HT was improved and the carrier mobility of OFETs was increased too.Meanwhile,the ion gel was used to be the dielectric layer so as to decrease the operating voltage of OFETs.The paper mainly focuses on the structure and material selection of flexible OFETs,the airflow assisted printing technology,fabrication and measurement of OFETs,and the OFETs’ application demostration.The major researches are summaried as follows:The working principle of OFETs was analyzed,and the influences of structures and materials on flexible OFETs’ performance were investigated.To meet the needs of large-scaled and integrated applications,OFETs with top-gate and bottom-contact configuration were determined.P3HT and ion gel were selected as semiconductor layer and dielectric layer to obtain flexible OFETs devices with high carrier mobility and low operating voltage,respectively.The shearing effect of airflow assisted printing fabrication method on P3HT solution was simulated to analyze the effectiveness of the proposed method.After establishing the airflow assisted printing system,influence of process parameters on the crystallization properties of P3HT films were studied.Experiment results showed that the crystallization performance of P3HT films was improved with the increase of moving speed of substrate and inlet pressure under the moving speed of 1.5-3.5 mm/s and the inlet pressure of 0-300 Pa.The flexible OFETs were manufactured,and the effects of substrate’s moving speed and airflow inlet pressure on OFETs’carrier mobility were analyzed.The experiment results showed that the carrier mobility of flexible OFETs was improved by increasing the substrate’s moving speed and airflow inlet pressure.Under the printing speed of 3.5 mm/s and the airflow inlet pressure of 300 Pa,flexible OFETs with carrier mobility of 2.527±1.194 cm2/V·s were obtained.The carrier mobility was～3.5 times than that of normal OFETs and their operating voltage were less than-1.5 V.The OFET based flexible humidity sensor,OFET based flexible sensor signal amplifier circuit and flexible pressure sensor based OFET on-off circuit array were fabricated,demonstrating the applications of OFETs in signal conversion,signal amplification and on-off circuit.The flexible humidity sensor had a sensitivity of 0.327 with good consistency,and its application in measuring human respiration,speech etc.was demonstrated.The signal amplification circuit amplified the signal of humidity sensor and pressure sensor by～1.5 times and～2.4 times,respectively.The paper shows that the airflow assisted printed P3HT semiconductive layer and the ion-gel dielectric layer can effectively improve the carrier mobility and reduce the operating voltage of OFETs,which provides a manufacturing scheme for large-area OFETs based flexible electronics,and further promotes its industrial applications.